Scanning Microscopy


The earthworm, Aporrectodea longa, which experiences an apparent obligatory physiological resting state (“diapause”) in the temperate Summer, was collected monthly from February through to October. Morphological examination of the chloragocytes, and quantitative electron probe X-ray microanalysis of their constituent chloragosome granules prepared by cryoultramicrotomy and air-dried/smearing, were undertaken over this period. Worms entered diapause in May, and emerged from it between August and September. The long-term energy stores in the form of lipid, in addition to the more usual polysaccharide (glycogen) reserves, were accumulated by early diapause; the lipid was gradually consumed during diapause. In addition, the structure and composition of the chloragosomes changed considerably during the annual cycle: there was an accumulation of Ca, P, Zn and S around the period of entry into diapause; Ca, P and Zn were mobilized from the granules as diapause progressed. The adaptive significance of these changes is discussed in the broad context of the different ecophysiological strategies evolved by stenohaline earthworms to resolve the problems posed by dry climatic conditions.

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